include_once

(PHP 4, PHP 5, PHP 7)

The include_once statement includes and evaluates
the specified file during the execution of the script.
This is a behavior similar to the include statement,
with the only difference being that if the code from a file has already
been included, it will not be included again, and include_once returns TRUE. As the name suggests,
the file will be included just once.

include_once may be used in cases where
the same file might be included and evaluated more than once during a
particular execution of a script, so in this case it may help avoid
problems such as function redefinitions, variable value reassignments, etc.

See the include documentation for information about
how this function works.

Since I like to reuse a lot of code it came handy to me to begin some sort of library that I stored in a subdire.g. "lib"

The only thing that bothered me for some time was that although everything worked all IDEs reported during editingthese useless warnings "file not found" when library files included other library files, since my path were given all relative to the corresponding document-root.

i already had a discussion with several people about "not shown errors"error reporting and all others in php.ini set to: "show errors" to find problems: the answer i finally found:if you have an "@include..." instead of "include..." or "require..('somthing') in any place in your code all following errors are not shown too!!!

so, this is actually a bad idea when developing because paser errors will be droped too:<?phpif(!@include_once('./somthing') ) { echo 'can not include';}?>